The present invention relates to motor vehicle sensors and actuators.
In order to comply with state and federal environmental regulations, most motor vehicles are now equipped with a carbon canister installed to trap and store petroleum fuel vapors from the carburetor bowl and/or the fuel tank. With the canister, fuel vapor is not vented to the atmosphere, but is instead trapped in the canister and then periodically purged from the canister into the engine where the fuel vapor is burned along with the air-fuel mixture.
Solenoid valves have been provided that are used to purge the fuel vapor from the carbon canister. Unfortunately, many of these valves are adversely effected by signal noise due to contact between the valve plunger and its corresponding valve seat. Moreover, many of these valves do not provide continuous flow at different valve positions and are unable to provide precise purging at engine idle, i.e., these valves are unable to accurately control the rate of flow through the valve.
As such, the present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A solenoid valve includes an outlet tube that forms an outlet passage, and a plunger stop. A plunger is slidably disposed within the solenoid valve between the outlet tube and the plunger stop. The plunger is movable between a closed position, wherein the plunger engages the outlet tube to block fluid flow through the outlet passage, and an open position, wherein the plunger is distanced from the outlet tube to permit fluid flow through the outlet passage. The solenoid valve further includes a coil that surrounds the plunger. The coil is energizable to bias the plunger between the closed position and the open position. Moreover, the plunger stop is configured so that the force of attraction between the plunger and the plunger stop is linearly proportional to the current applied to the coil.
In a preferred embodiment, the force of attraction between the plunger and the plunger stop is independent of the position of the plunger. Preferably, the plunger stop includes a solid base. A tapered wall extends from the solid base. In a preferred embodiment, the tapered wall defines a stop angle that is in a range from eleven degrees and sixteen degrees (11xc2x0 to 16xc2x0). Moreover, the valve includes a plunger sleeve that surrounds the plunger and a main air gap is formed between the plunger sleeve and the plunger stop. Preferably, the main air gap is in a range from one-half of a millimeter to two millimeters (0.5 mm to 2.0 mm). The solenoid valve also includes a plunger tube between the plunger and the plunger sleeve. A secondary air gap is formed between the plunger and the plunger stop. In a preferred embodiment, the secondary air gap is in a range from three tenths of a millimeter to fifty-five hundredths of a millimeter (0.3 mm to 0.55 mm).
In another aspect of the present invention, a solenoid valve includes an outlet tube that forms an outlet passage and a plunger stop. The plunger stop includes a solid base and a tapered wall that extends there from. A plunger is slidably disposed within the solenoid valve between the outlet tube and the plunger stop. The plunger is movable between a closed position, wherein the plunger engages the outlet tube to block fluid flow through the outlet passage, and an open position, wherein the plunger is distanced from the outlet tube to permit fluid flow through the outlet passage.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: